package com.web.util;

import java.security.MessageDigest;

public class MD5 {
	private MessageDigest md5;
	private static MD5 Instance;

	/***************************************************************************
	 * Constructs the MD5 object and sets the string whose MD5 is to be
	 * computed.
	 * 
	 * @param inStr
	 *            the <code>String</code> whose MD5 is to be computed
	 */
	public synchronized static MD5 getMD5Instance() 
	{
		if (Instance == null)
			Instance = new MD5();
		return Instance;
	}

	private MD5() 
	{
		try 
		{
			this.md5 = MessageDigest.getInstance("MD5");
		} 
		catch (Exception e) 
		{
			e.printStackTrace();
		}
	}

	/** */
	/**
	 * Computes the MD5 finger print of a string.
	 * 
	 * @return the MD5 digest of the input <code>String</code>
	 */
	public String compute(String inStr) {
		try {
			// convert input String to a char[]
			// convert that char[] to byte[]
			// get the md5 digest as byte[]
			// bit-wise AND that byte[] with 0xff
			// prepend "0" to the output StringBuffer to make sure that we don't end
			// up with
			// something like "e21ff" instead of "e201ff"
	
			char[] charArray = inStr.toCharArray();
			byte[] byteArray = new byte[charArray.length];
	
			for (int i = 0; i < charArray.length; i++)
				byteArray[i] = (byte) charArray[i];
	
			byte[] md5Bytes = this.md5.digest(byteArray);
	
			StringBuffer hexValue = new StringBuffer();
	
			for (int i = 0; i < md5Bytes.length; i++) {
				int val = ((int) md5Bytes[i]) & 0xff;
				if (val < 16)
					hexValue.append("0");
				hexValue.append(Integer.toHexString(val));
			}
	
			return hexValue.toString();
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}
}
